As well-known in the art, due to negative influence of the prevalence of computers and the Internet, the possibility of leakage of secret data of enterprises or clients' personal information is on the rise, and substantially, a corresponding financial loss tends to grow annually. Particularly, data managed in enterprises is leaked by insiders in many cases, and it has become a social issue in addition to the problem of the enterprises themselves because such an internal data leakage involves client's personal information, as well as secret data of enterprises.
Conventionally, in order to prevent such a data leakage, techniques for monitoring data leakage points and preventing data from being transmitted from a computer to an external device or a different computer via the leakage points in a network have been used. However, in line with the acceleration of the development of information communication technologies, various types of external devices have been presented, and leakage points have also been diversified. Therefore, blocking leakage points for preventing a data leakage and protection has a limitation.
In particular, when an insider intends to leak data created by him self or corrected in his computer, it would be very difficult to prevent a data leakage.
[Patent document 1] U.S. Patent Publication No. 2008-0072000